Movements of large patterns elicit ocular following (OFR) at ultra-short latency (monkeys, <60 ms; humans, <80 ms), and the very earliest responses can be elicited only by images moving in the plane of fixation: images with binocular disparities exceeding a few degrees are ineffective (Busettini et al., 1996). In past studies, only one pattern was present, and we now report the effect on the initial OFR (of two monkeys and two humans) of introducing a second (interfering) pattern that moves with conflicting motion in the same or a different depth plane. Visual stimuli, produced by back-projection onto a tangent screen, consisted of regularly spaced horizontal bands (3.36 degrees thick) of random dots that could be moved horizontally to induce ocular following. However, the bands were organized into two groups such that alternate bands moved always together and opposite in direction to the intervening bands. Using multiple projectors and crossed polarizers to confine images to one or the other eye, one set of "drive" bands was imaged always in the plane of fixation, while the other set of "interfering bands was imaged within or outside the plane of fixation by adjusting their horizontal disparity (range, 0-12.8 degrees crossed and uncrossed). Trials started with all images stationary in the plane of the screen. In the wake of 10 degrees centering saccades, shutters blanked the scene for 15 ms, after which the two sets of bands were revealed to be moving at 40 degrees/s in opposite directions. For all subjects, the initial OFR induced by the motion of the "drive" images showed strong dependence on the disparity of the "interfering" images. Based on measures of the change in version, initial OFR was weakest when the disparity of the interfering images was <0.5 degrees and increased to a maximum as their disparity increased to 2-5 degrees; in some cases, response measures declined with further increases in disparity (Mexican hat vs. bell profile). Thus, the "interfering" images were most potent in degrading responses to the drive images when in the same depth plane and became less potent when they were positioned at other depth planes. These data indicate that initial OFR can use binocular disparity to distinguish images moving in the plane of fixation from those moving in other depth planes. The data for monkeys and humans were the same in all essentials, indicating that the monkey provides an excellent animal model.